1. Field of the Invention
The present invention relates, generally, to instruments for measuring and monitoring the pressure exerted on a person's skin, and, more particularly, to pressure measuring and monitoring instruments which are programmable and provide indication when the level and duration of pressure reach certain values.
2. Description of Related Art
The skin of people confined to a bed or wheelchair is susceptible to decubitus ulcers, commonly referred to as pressure sores or bed sores. This susceptibility is generally due to a level of pressure being exerted on an area, particularly a bony prominence, for an excessive duration of time. The pressure occludes the capillaries, cutting off the blood supply, causing necrosis of the tissue. Ordinarily, people with normal range of movement and sensation adjust or shift their weight to relieve such pressure prior to the formation of such sores. People who are bedridden, though, although they may have sensation, may not have an adequate range of movement and, therefore, cannot as easily adjust or shift their weight. People confined to a wheelchair, paraplegics for example, may be able to adjust or shift their weight but do not have sensation to indicate that it is time to do so. People with insensate feet, diabetics for instance, develop pressure sores which may ultimately result in amputation. Additionally, a person's susceptibility to the formation of such sores is dependent, to a certain extent, on tissue condition.
The most effective way to ameliorate the impact of pressure or bed sores is to preclude their formation. For bedridden persons this requires another person, like a nurse or other care giver, to periodically move or shift the bedridden person at the first sign of discomfort. For paraplegics and diabetics, though, because of their insensate condition, there is no sign of discomfort. In addition, diabetics with insensate feet tend to develop calluses at the pressure points on their feet aggravating the condition. Therefore, some external indication must be communicated to the paraplegic and the diabetic that it is time to shift or move or get off their feet. For the paraplegic, simply periodically raising themselves slightly from the wheelchair seat by pushing themselves up using their arms on the wheel chair handles or wheels ("pressure-relief") can preclude the formation of pressure sores. For the diabetic, sitting or in some way removing the weight from the foot achieves the same result. Although pressure-relief is simple to perform and very successful in the prevention of pressure sores, to be effective, the practice must become a life-long habit. A significant number of paraplegics, though, abandon the practice after leaving a hospital. This is due, mainly, to their lack of discipline and the possible embarrassment that may be caused by traditional reminder devices. For diabetics, there exists no suitable device or system to remind of the need for a pressure relief.
It is necessary, therefore, not only to adequately train a person in a pressure-relief technique but also to provide the person with a device that continually reinforces such training to instill in the person a life-long behavioral pattern and one that operates in accordance with a person's specific physical characteristics and needs. Inherent in this is the interaction of a physician, clinician and/or therapist who can adjust the device according to the specific needs, train the person in the proper pressure-relief technique and review, monitor and analyze the progress the person is making in relieving the pressure. This requires not only a means for monitoring the level and duration of pressure and indicating when relief must be performed, but also a means for recording and logging the person's pressure-relief attempts and successes.
U.S. Pat. No. 4,554,930 to Kress (abandoned), teaches a pressure sensing device and method for preventing ulcer formation. The device and method in Kress, though, are based on a fixed, predetermined level of pressure and time which cannot be changed. In other words, it is a one-size-fits-all device. The device is not programmable nor does it record the person's attempts to relieve the pressure and the duration of such pressure or relief In addition, there is no ability for a physician, clinician or therapist to review or analyze the activity of the person. There is no way to feed back to the person or the physician information which discloses and details the efforts of the person in relieving the pressure.
The need to adjust or program a device or system to fit a patient's particular circumstances was fully explained by Charles T. Merbitz et al., Wheelchair Push-ups: Measuring Pressure Relief Frequency, Arch Physician Medical Rehabilitation Vol. 66, July 1985. On page 9, the authors discuss how their findings suggest the need for an "individual prescription of inter-lift-off intervals for a given patient". For their study the authors utilized a rudimentary device involving air bladders with a lever to indicate when a certain threshold was reached. The device was not programmable or adjustable for a particular patient, but adequately illustrated the need for same.
U.S. Pat. No. 5,253,656 to Rincoe et al., teaches an apparatus and method for monitoring pressure between the surface of a body part and a contact surface. The device in Rincoe et al. teaches the reading of a plurality of pressure sensors by a microcomputer, through interface circuitry, which then develops a force profile from the readings. The pressure sensors are arranged in a column and row array and are read through a multiplexing process utilizing unique addresses for each sensor. The microcomputer, a personal computer, controls the apparatus with instructions inputted through a keyboard with the force profile visually presented on the computer display. The apparatus, therefore, is designed such that the personal computer must be attached to the pressure sensors in order for it to operate. Accordingly, the subject, usually a patient, is continuously tethered to the computer eliminating any mobility and restricting the times in which the apparatus actually performs any monitoring.
U.S. Pat. No. 5,042,504 to Huberti teaches a device for monitoring loads exerted on parts of the body. The Huberti device requires that a load-related parameter be measured and raw data representing that parameter be generated. The raw data is the output from the sensor corresponding to the force measured thereby which is entered into memory and plotted over time. The raw data is compared to analysis data and reference data, also inputted into memory, to produce a visual representation comparing the raw data, analysis data and reference data. This type of complex data inputting and comparing is appropriate for applications involving dynamic loading of extremities during rehabilitation. In fact, Huberti is specifically drawn to foot weight sensing where load profiling is necessary in order to assure the optimal healing of injured legs or the proper placement and use of prosthetic devices. It does not provide the required utility for pressure or bed sore prevention.
U.S. Pat. No. 5,619,186 to Schmidt et al. describes a foot weight alarm device that senses the dynamic forces exerted on a foot, develops a digital value corresponding to such force and provides an alarm when the force exceeds a certain level or range. The device of this patent, though, does not take into account any duration of loading or non-loading and like the device in Huberti does not provide the appropriate utility for pressure sore prevention.
Accordingly, a need exists for a system and device which can be used by a physician, clinician and/or therapist to develop the appropriate pressure level and duration for a particular person and to train a person in the proper technique and timing of a pressure-relief, which provides to the person an indication of the need for a pressure-relief and does so in an unobtrusive and non-embarrassing manner; which provides a record or log of the person's pressure-relief attempts and successes so that the person's pressure relief activities can be reviewed and the training periodically reinforced; and is light weight, mobile and easy to use.